OnPreRender method of GridView control

Question

   I was using a reflector and came up on this method OnPreRender() of GridView web control.
 
   protected internal override void OnPreRender(EventArgs e)   { 
       base.OnPreRender(e); 
       if (this.DetermineRenderClientScript() && (this.Page != null)) 
       { 
           ........ 
               clientScript.RegisterClientScriptResource(typeof(GridView), "GridView.js"); 
           ........ 
       } 
   }
 
 Its calling JavaScript (GridView.js).

 Can any one explain the usage of this .js file.

 Can we override the file prior rendering of GridView.